get single-click double-click and triple-click with rxjs

click.js

//https://stackoverflow.com/questions/37310640/rxjs-buffer-how-to-group-multi-click-events-as-stream/51547034#51547034
const btn = document.querySelector('#btn');
const click$ = Rx.Observable.fromEvent(btn, "click");

const trigger$ =
  click$.exhaustMap(r =>
    click$
    .take(2)
    .last()
    .race(click$
      .startWith(0)
      .debounceTime(500)
      .take(1))
  );


click$
  .buffer(trigger$)
  .map(l => l.length)
  .map(x => ({
    1: 'single',
    2: 'double',
    3: 'tripple'
  }[x]))
  .map(c => c + '-click')
  .subscribe(log);